1. Field of the Invention
This invention relates to a building component of panel form, that is, a building component having substantially two-dimensional form and used as a surface or skin building component, such as a facade component, internal or external wall component, floor component or roof or ceiling component.
2. Prior Art
U.S. Pat. No. 3,376,834 shows a heat-insulating structure which is useful as a wall, floor or roof or similar building structure. For the purpose of this specification, this known structure is simply termed "wall".
This prior wall comprises a porous, air-permeable layer of heat-insulating material, such as mineral or slag wool. On one or both sides of the porous layer there is a finely perforated sheet, such as a plastic film. When the wall is used to insulate against loss of heat from a room to a space at a lower temperature, a small pressure differential is maintained across the wall to cause air to flow through the porous layer and the perforated sheet from the colder space towards the room, that is, from the colder side towards the warmer side. The finely perforated sheet serves to maintain the pressure differential and to ensure that the air flow is substantially uniformly distributed over the entire area of the wall and passes through the porous layer substantially perpendicularly to the wall.
The inwardly flowing air will be heated by the outwardly directed heat flow and thus will carry at least a part of the outwardly flowing heat back towards the warmer side of the wall. If the air flow is fairly uniformly distributed, it is possible to obtain a very efficient heat insulation even if the porous layer is relatively thin and the air flow and the pressure differential are relatively small, e.g. a flow on the order of 1 cubic meter per hour per square meter of wall area, and a pressure on the order of a few millimeters of water pressure.
In practice, the side of the wall facing the room, the inner side is provided with a layer which is impermeable to air flow and formed of hardboard, for example. This impermeable layer is slightly spaced from the porous layer so that a narrow clearance or air space is formed between the porous layer and the impermeable layer. The air space is connected to a suction fan producing the necessary air flow. Naturally, the outer side of the porous layer also has to be exposed so that the air entering the porous layer can be distributed over the entire area thereof. To this end, the outer side of the wall may have a facade panel which is slightly spaced from the porous layer and which preferably is impermeable to air flow.
In order that the wall may provide the desired heat insulation with minimum size of the fan, it is of course necessary to ensure that all of the air that the fan sucks from the air space at the inner side of the wall passes through the porous layer, that is, to ensure that air can enter the air space only from the space at the outer side of the porous layer. As is readily understood, a crack or a hole in the layer separating the air space from the room may mean that the air is partly or wholly sucked from the room into the air space instead of being sucked exclusively through the porous layer.
It is necessary, therefore, to construct the wall in such a manner as to ensure that the air space remains sealed in airtight manner throughout the life of the wall. For example, displacements caused by distortions of the building or by fluctuations of the moisture content and/or temperature must not destroy the air-tightness.
An efficient production of walls of the above-described kind therefore can only be ensured if the walls are constructed from factory-made standardized units, e.g. of a height equal to room height and a width corresponding to standard widths of building boards. Since such wall units have a thickness equal, or almost equal, to that of the finished wall, the transport from the factory to the building site requires a considerable transportation capacity; during the transport the elements also have to be well protected against mechanical damage. Moreover, such standardized units restrict the options of the building designer.